With rise in deployment of Long term Evolution (LTE) and LTE advanced (LTE-A), small cells using low power nodes such as a Pico cell and a Femto cell are considered promising to cope with mobile traffic explosion. A small cell using a low power node which has transmission power (Tx) lower than a macro node and Base Station (BS) classes is preferred for hotspot deployments in indoor and outdoor scenarios. The small cell enhancement for Evolved Universal Mobile Telecommunication System (UMTS) Terrestrial Radio Access Network (E-UTRAN) and E-UTRA focuses on additional functionalities for enhanced performance in hotspot areas for indoor and outdoor using the low power nodes. The small cell enhancement can be expected to support significantly increased user throughput for both downlink and uplink with main focus on typical user throughput given a reasonable system complexity. The small cell enhancement is expected to target the capacity per unit area (e.g. bps/km2) to be as high as possible, for a given user and small cell distribution, typical traffic types and considering a reasonable system complexity. In LTE Release-11 specification a UE can be carrier aggregated by carriers from different frequency bands. The UE is carrier aggregated with at least one first serving frequency served by a primary eNB and at least one second serving frequency served by a secondary eNB. This carrier aggregation of the UE is called as inter-eNB carrier aggregation and the UE. Dual Connectivity involves two eNBs in providing radio resources to a given UE (with active radio bearers), while single S1-MME termination point exists for an UE between a MME and the E-UTRAN. The E-UTRAN architecture and related functions to support Dual Connectivity for E-UTRAN is further described in TS 36.300.
In existing security mechanisms supporting inter-carrier aggregation at the UE, authentication and authorization are performed using the authentication and key agreement procedure (AKA) defined for the evolved Universal Terrestrial Radio Access (E-UTRAN) in the LTE Networks. An initial security key is derived by the Mobility Management Entity (MME) in the core network and sent to a primary eNB. During an inter-eNB (S1 or X2-initiated) handover, the primary eNB derives the security key for a secondary eNB, using a base security key. The same security key is used for deriving further keys, which one of the key is used for user plane data protection.
During a handover (HO), the unused next hop (NH) parameters or an existing security key associated with the primary eNB can be used for deriving the base security key. For forward, security, a new security key for the secondary eNB can be derived using a vertical key derivation at the anchor eNB using unused Next Hop (NH) parameters. The unused NH parameters may not be used always, and the existing security key may be used as for deriving the security key for the drift eNB. The use of the existing security key for communication between the drift eNB and the UE may not provide adequate key separation, resulting in security compromise.
Further, if the primary eNB derives security key for the secondary eNB using an existing security key, then the key repetition will occur. Further, each time the secondary eNB is removed and added again for supporting dual connectivity, the security key generated may be repeated. Further, key stream repetition is highly possible when the existing security mechanism defined in TS 33.401 is used for dual connectivity and leads to exposing the user plane to security attacks, which needs to be avoided.
In additional to key repetition, the security capabilities and/or local configuration of the secondary eNB may be different from primary eNB. Hence, the UE may need to use different cryptographic algorithms for communicating with the secondary eNB. The establishment of security context between the secondary eNB and the UE requires knowledge of the security algorithms supported and selected by the secondary eNB.
The above information is presented as background information only to help the reader to understand the present invention. Applicants have made no determination and make no assertion as to whether any of the above might be applicable as Prior Art with regard to the present application.